1. Field of the Invention
The present invention relates to a transverse electric liquid crystal display device, and more particularly to a transverse electric liquid crystal display device free from unevenness of display due to static electricity.
2. Description of the Related Art
In general, a liquid crystal panel is designed to have a liquid crystal material sealed in the gap between two glass substrates. A liquid crystal panel is composed of a rear-side glass substrate that has a thin-film transistor (TFT) formed on its liquid-crystal-side surface (hereafter referred to as the TFT-side glass substrate) and a glass substrate that has a color filter disposed between its surface and the liquid crystal material (hereafter referred to as the color-filter-side glass substrate). FIG. 1 is a top view and side views illustrating the structure of a conventional liquid crystal panel. As shown in FIG. 1, a conventional liquid crystal panel is composed of two glass substrates of different sizes bonded together. On the liquid-crystal-side surface of a rear-side glass substrate 30, a TFT for controlling turning ON/OFF of a liquid crystal picture element 33 is formed. By composing the liquid crystal panel of two glass substrates of different sizes, it is possible to prevent an input terminal 32 for feeding a signal to a picture element 33 from being covered by a display-surface-side glass substrate 31. Accordingly, the rear-side glass substrate 30 is made larger in size than the display-surface-side glass substrate 31 in which a color filter is disposed. In this way, the two glass substrates are bonded together so that they have a projection 34a and a projection 34b, the projections 34a and 34b being so formed as to protrude horizontally and vertically, respectively, from the TFT-side glass substrate 30 over the color-filter-side glass substrate 31. In order to feed a signal from outside to the liquid crystal panel, generally, as shown in FIG. 1, the glass substrate 30 needs to be so constructed that its two, longitudinal and lateral side edges, along which the input terminals 32 are formed, are left uncovered by the display-surface-side glass substrate 31. Even though the liquid crystal panel is specially designed, at least one side edge of the glass substrate 30 needs to be left uncovered. In the liquid crystal panel as indicated as an area 35, the two glass substrates are superimposed together at their side edges excluding those having the projections 34a or 34b. 
In the liquid crystal display device, the two substrates are each provided with an electrode in order to generate an electric field therebetween. This makes it possible to control orientation of liquid crystal molecules in the liquid crystal material sealed in the gap between the two glass substrates. As a result, a display image is formed. When the direction of the electric field is assumed to be the lengthwise direction, the transverse electric liquid crystal panel has electrodes arranged in a row only along the surface of the TFT-side glass substrate. In this construction, orientation of the liquid crystal molecules is controlled by applying to the liquid crystal molecules an electric field in the transverse direction. Accordingly, in a case where static electricity is applied to the surface of the TFT-side glass substrate or the color-filter-side glass substrate and then the electrostatic charge remains on the glass surface of the substrate, an electric field is generated in the lengthwise direction. This causes the liquid crystal molecules to be oriented in a fixed direction. As a result, it is not possible to control orientation of the liquid crystal molecules properly, and this leads to unevenness of display. As will be understood from the foregoing, a transverse electric liquid crystal panel tends to suffer from degradation of display quality due to static electricity, and therefore it necessitates a means for eliminating the undesirable effects of static electricity.
Conventionally, a construction is known in which, to absorb static electricity, a transparent conductive film is formed on the surface of the display-surface-side liquid crystal panel, and this transparent conductive film is connected to the casing with a conductive spacer or the like. For example, Japanese Patent Laid-open Publication No. Hei 9-258203 proposes a liquid crystal panel of this type (a conventional example 1). FIG. 2 is a sectional view illustrating the structure of the transverse electric liquid crystal display device of the conventional example 1. As shown in FIG. 2, the transverse electric liquid crystal display device of the conventional example 1 is provided with a liquid crystal panel 101 and a circuit board 107. The liquid crystal panel 101 is located above a backlight illumination device 113 and is sandwiched between polarizing plates 105a and 105b. The circuit board 107 is arranged adjacent to the liquid crystal panel 101. The liquid crystal panel 101 is composed of a TFT-side glass substrate 102 and a color-filter-side glass substrate 103. The TFT-side glass substrate 102 is disposed on the backlight-illumination-device 113 side of the display device and has an area larger than the color-filter-side glass substrate 103. These two glass substrates are superimposed on each other so as to have a projection. The color-filter-side glass substrate 103 has a transparent conductive film 104 formed between its surface and the polarizing plate 105b that is located thereabove.
The projection provided in the liquid crystal panel 101 is built as a pressure-contacting portion 110 that acts as the connection between the TFT and a TCP (tape carrier package) 106 for driving the TFT. The TCP 106 has its one end connected to the pressure-contacting portion 110 and the other end connected to the circuit board 107. The polarizing plate 105a and the polarizing plate 105b, which are formed on the bottom surface of the TFT-side glass substrate 102 and the top surface of the color-filter-side glass substrate 103, respectively, are used to polarize the light coming from the backlight illumination device 113 that illuminates the liquid crystal panel 101 from the rear. Moreover, the display-surface-side polarizing plate 105b has an area smaller than the color-filter-side glass substrate 103. This allows the transparent conductive film 104, which is provided underneath the polarizing plate 105b, to be exposed so as to be connected to a casing 109 via a conductive spacer 112. In this way, even if the display surface is brought into contact, for example, with a user, and then the static electricity therefrom is applied to the transverse electric liquid crystal panel 101, it is possible to discharge the remaining static electricity into the casing 109.
Moreover, Japanese Laid-open Publication No. Hei 11-185991 proposes a technique to protect electronic equipment against static electricity by making use of a ground of a circuit board mounted in a liquid crystal display device (a conventional example 2). According to the conventional example 2, electronic equipment provided with a panel, for example, a liquid crystal display panel, has a transparent conductive member formed on its panel surface. In this example, by connecting this transparent conductive member to the ground of the circuit board incorporated in the electronic equipment by the use of an electric conduction means, it is possible to discharge the static electricity applied to the panel surface through the transparent conductive member via the electric conduction means into the ground of the circuit board. FIG. 3 is a sectional view illustrating the structure of the liquid crystal display device of the conventional example 2.
As shown in FIG. 3, inside a lower case 201 and an upper case 202 are arranged a main-circuit board 203, a sub-circuit board 204, and a liquid crystal panel 205. The sub-circuit board 204 and the liquid crystal panel 205 are located above the main-circuit board 203. Underneath the liquid crystal panel 205 is formed an EL (electro-luminescence) 207 built as a backlight, a shielding plate 208, and a flexible wire 209. The main-circuit board 203, disposed below the components described just above, has a plurality of electronic components 213 of different types formed on its top and bottom surfaces. The liquid crystal panel 205 is supported at its periphery by a panel holder 206. Moreover, a transparent conductive sheet 216 is stuck onto the top surface of the liquid crystal panel 205. Above the transparent conductive sheet 216 is disposed printing glass 211. A conductive sheet 217 with conductive adhesive has its one end stuck onto the top surface of the transparent conductive sheet 216 formed at the end of the liquid crystal panel 205, and the other end crimped to a ground 218 disposed on the ground-potential side of the power source of the sub-circuit board 204. The printing glass 211 has its end kept in direct contact with the upper case 202. Between the upper case 202 and the conductive sheet 217 with conductive adhesive formed on the top surface of the transparent conductive sheet 216 is disposed a compressed sponge 215. This helps establish satisfactory electrical connection among the relevant components.
However, a liquid crystal display device, like the above-described conventional example 1, that is so designed that the overlapping area between the glass substrates constituting the liquid crystal panel is used as a junction, has the following disadvantage. In this construction, the two glass substrates have a gap secured therebetween for containing a liquid crystal material. Therefore, in a case where the transparent conductive film is connected to the casing with, as a connecting means that constantly applies pressure to the liquid crystal panel, a conductive spacer or a contact piece, variation in the gap secured in the liquid display panel is unavoidable around the junction and its periphery. This leads to unevenness of display. In addition, since the casing, which is susceptible to external oscillation and shock, makes contact with the overlapping area between the two glass substrates, the external oscillation and shock applied to the casing causes the gap between the two glass substrates to vary periodically. As a result, wave-like irregularities in display occur relative to the junction between the casing and the liquid crystal panel.
Similarly, in the liquid crystal display device of the conventional example 2, connection is established by making use of the overlapping area between the two glass substrates constituting the liquid crystal panel. This causes the junction to be subjected to pressure, whereby only the part to which pressure is applied in the gap between the two glass substrates becomes narrower. As a result, the optical characteristics of the liquid crystal material sealed in the gap between the two glass substrates are disturbed, and this leads to unevenness of display.
An object of the present invention is to provide a transverse electric liquid crystal display device in which unevenness of display is satisfactorily suppressed by protecting the transverse electric liquid crystal panel against static electricity and by improving the connection reliability.
A transverse electric liquid crystal display device according to the present invention includes: a transverse electric liquid crystal panel; a circuit board arranged adjacent to the transverse electric liquid crystal panel; a semiconductor integrated circuit chip being connected to said transverse electric liquid crystal panel and said circuit board; and a casing for housing said transverse electric liquid crystal panel, said circuit board, and said semiconductor integrated circuit chip. The transverse electric liquid crystal panel comprises: a first transparent substrate; a second transparent substrate; a liquid crystal material sealed in a gap between said first transparent substrate and said second transparent substrate; a driving electrode and thin-film transistor being inputted a signal from said thin-film transistor and driving said liquid crystal material by generating electric field in a direction parallel to said first transparent substrate, said electrode and said thin-film transistor being formed on a liquid-crystal-side surface of said first transparent substrate; and a color filter disposed between said second transparent substrate and said liquid crystal material. The display-surface-side transparent substrate, of the two transparent substrates constituting the transverse electric liquid crystal panel, is bonded to the other rear-side transparent substrate so as to have a first projection. The first projection is so formed as to protrude horizontally from the display-surface-side transparent substrate over the rear-side transparent substrate. A transparent conductive film for absorbing static electricity is formed on a display-surface-side surface of the display-surface-side transparent substrate. The transparent conductive film is so formed as to extend over the first projection and being grounded by a conductive member.
In the transverse electric liquid crystal panel according to the present invention, on the surface of the display-surface-side transparent substrate is formed a transparent conductive film for absorbing the static electricity remaining on the display surface. Since this transparent conductive film is grounded, it is possible to protect the transverse electric liquid crystal panel against static electricity. Moreover, the transparent conductive film has its junction formed in the projection that is so formed as to protrude horizontally from the display-surface-side first transparent substrate. This makes it possible, before and after connection is established, to protect the gap between the first and second transparent substrates against pressure around the junction, and thus prevent unevenness of display.
Either the first transparent substrate having a driving electrode and a thin-film transistor formed therein or the color-filter-side second transparent substrate may be disposed on the display-surface side of the transverse electric liquid crystal device.
The transparent conductive film provided in the first projection may be connected to the ground of the circuit board by the conductive member.
It is possible to realize the first transparent substrate having a driving electrode and a thin-film transistor formed therein as the display-surface-side transparent substrate. In this case, it is preferable that the input terminal of the thin-film transistor formed on the back side of the first projection of the first transparent substrate be connected to the semiconductor integrated circuit chip, and that the transparent conductive film provided on the display-surface side of the first projection be connected to the ground of the circuit board by the conductive member. By doing so, it is possible to connect the transparent conductive film to the circuit board by making use of the back side of the junction between the integrated circuit chip and the first transparent substrate. This helps reduce the distance (hereinafter referred to as xe2x80x9cthe framexe2x80x9d) between the display area of the liquid crystal display device and the very end of the components housed in the casing of the display device.
It is also possible to realize the color-filter-side second transparent substrate as the display-surface-side transparent substrate. In this case, it is preferable that the transparent conductive film provided on the display-surface side of the first projection of the second transparent substrate be connected to the ground of the circuit board with the conductive member, that the first transparent substrate be bonded to the second transparent substrate so that it has a second projection, the second projection being so formed as to protrude therefrom in a direction perpendicular to the first projection, and that the input terminal of the thin-film transistor formed on the second-transparent-substrate-side surface of the second projection of the first transparent substrate be connected to the semiconductor integrated circuit chip. By doing so, it is possible to ground the transparent conductive film by making use of an area away from the semiconductor integrated circuit chip. As a result, in a case where the semiconductor integrated circuit chip is driven into malfunction, it can be replaced with another with ease without being disturbed by the conductive member for connecting the transparent conductive film to the ground of the circuit board.
The transparent conductive film provided on the display-surface-side of the first projection may be connected to the casing by the conductive member.
The conductive member and its corresponding portion may be connected to each other with an anisotropic conductive tape.
The conductive member may be selected from the group consisting of a conductive cable, a conductive tape to which adhesive containing a conductive agent is applied, a conductive adhesive, a conductive rubber, and a contact piece.
The conductive member may be realized by the use of a conductive cable, and at least the transparent conductive film is soldered to the junction of the conductive cable by ultrasonic solder.
The nature, principle, and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.